The design and construction of a cable or wiring harness for use in an aircraft engine or similarly complex application must meet many specific criteria. A typical wiring harness used in an aircraft engine will follow a very complex path around many components of the engine and often will include many locations where smaller groupings of wires split off from the main group to follow complex paths of their own.
Further, design considerations often demand that the tolerances of the individual lengths of a complex wiring harness be on the order of a quarter of an inch or less. In some instances a wiring harness may include a significant number of wires such that the diameters of some of the wire groupings may be two inches or more. A wiring harness which varies slightly from the acceptable tolerances can result in a considerable amount of wasted engine assembly time, since the installation of a wiring harness may require numerous man hours before it is determined that a wiring harness is unacceptable.
Wiring harnesses are constructed on a layout board or unit which provides a guide to assist in sizing the wiring harness. However, the design and construction of the layout board is often very difficult. Usually a prototype engine for which a wiring harness is being constructed is located in a different plant than the layout board, and the size and weight of a conventional layout board makes transportation of the board impractical. Conventionally, a prototype wiring harness is constructed which follows the required path around the engine with the required wiring groups splitting off as necessary. Since it is usually not feasible to send off the prototype wiring harness for use as a model for the construction of a layout board, measurements are made of the prototype wiring harness and the measurements are, in turn, used to construct the layout board. Most often the complexity of the wiring harness and difficulty to accurately measure a large and complex wiring harness requires that several iterations of the layout board design take place until a suitable layout board is completed.
Many conventional layout boards are made of large sheets of plywood with nails used to identify locations where a wiring harness would require a split into certain wire groups. Other wood designs included layout boards with raceways machined into blocks of wood mounted on a plywood sheet. While these machined layout boards are more accurate than the nail design, they are very expensive, take an extremely long time to construct, and are not readily changeable. Still other assembly boards are constructed of sections of extruded aluminum stock which are secured together with arms or branches typically extending off a main trunk to form the appropriate configuration. These aluminum layout boards are very heavy, very expensive, take a long time to build, and are difficult to change, but generally offer accuracy and repeatability in the construction of a wiring harness. Another problem with conventional layout boards is that they are bulky and not easily stored.
It would be desirable to provide a layout board or unit that could be transported unassembled to the site where a prototype engine was being developed and there assembled according to the proper dimensions of the prototype wiring harness. The layout unit could then be transported back to the wiring harness manufacturing facility and reassembled easily, quickly and accurately to the dimensions of the prototype wiring harness so as to minimize the number of design iterations necessary to produce an acceptable wiring harness layout assembly unit design. An additional desire would be to provide a layout kit which could be disassembled and reused for the construction of a different wiring harness once one type of harness had been completed.